A lone protester steps into the path of an oncoming tank near Tahrir Square as demonstrations continued for a sixth straight day, January 30, 2011, in Cairo, Egypt.

Could the popular revolt against authoritarian regimes of the Middle East ever spread to China, the world’s most populous nation? And if so, does the United States have a policy to deal with it?

The ticklish question has been hovering in the background since the “Jasmine Revolution” street uprising toppled the president of Tunisia two weeks ago. It has only gained in urgency as the demonstrations spread to Yemen, Jordan and then Egypt — threatening President Hosni Mubarak’s near-30-year-grip on power.

A Chinese blogger first posed the query to President Obama’s chief Asia expert during a videoconference from the White House Situation Room with eight Mainland bloggers.

“In my view, many Chinese netizens and intellectuals believe that China’s future is Tunisia-ization,” noted the Beijing-based blogger, 2Keqi, in the Web chat with Jeffrey Bader, the National Security Council’s (NSC) senior director for Asian affairs. “Does the American government make this same assessment and does it have a policy plan” in the event that China takes such a turbulent path?

Bader and another official, Ben Rhodes, deputy NSC adviser for strategic communications, declined to answer directly, instead repeating the administration’s oft-stated position about the importance of human rights and the need to let people “realize their own aspirations.”

The question came up again last Friday at the White House news briefing, posed to press secretary Robert Gibbs — who similarly declined to engage.

But at a time when many Americans have come to view China — with its double-digit economic growth and huge investments in infrastructure and energy technologies — in terms of the challenges it poses to the United States’ position as the world’s pre-eminent economic power, many here see the country’s closed political system as unsustainable and a key vulnerability restricting its leaders’ grand ambition.

“America’s understanding of China is very limited,” the blogger, 2Keqi, told Bader and Rhodes. Many Chinese, he added, find it “extremely difficult to accept the idea that the 21st century is China’s century.”

It is an issue the Chinese authorities clearly care about, too. Chinese Internet users have been largely barred from making comments about the ongoing popular revolt in Egypt, as Beijing’s Communist rulers tread a fine line between allowing generally unfiltered news reports of the protests while also discouraging the idea that the uprising may bring democracy to the Arab world’s largest country.

Online news sites typically allow readers to have comments and form discussion groups after articles are posted, but that service has been disabled since the Egyptian protests began.

Also, the search engines on some of the most popular micro-blogging sites turned up no results for the words “Egypt,” “Cairo,” “Tunisia” and “Jasmine Revolution.” Users instead received a message saying the search result could not be displayed “because of the relevant law, regulations and policy.” Even searches for the word “jasmine” turned up no results.

The main Chinese newspapers all carried front-page stories about the protests, including photographs, but largely without any analysis or editorial comment. Much of the recent coverage has focused on the looting and the breakdown of order in Egyptian cities, without much explanation of the root causes of the unrest.

In the only official commentary on the uprising, the Chinese foreign minister spokesman, Hong Lei, said on Sunday, “Egypt is a friend of China and we hope Egypt will return to social stability and normal order as soon as possible.”

One editor of an online news site said the Party’s Propaganda Department, China’s main censorship organ, asked his outlet only to use news from Egypt provided by Xinhua, the official government news agency.

Still, some local micro-blogging sites — the Chinese equivalent of Twitter — have been following events in Egypt closely, often finding ways around the official controls. “The Netizens are quite excited by what’s happening in Egypt,” said Zhang Lifan, a historian who has studied the history of the Chinese Communist Party.

Zhang said he was able to browse through photographs from Egypt and found “those scenes are very similar to what happened in Beijing 20 years ago” — a reference to the Chinese army’s crackdown on pro-democracy students and demonstrators at Tiananmen Square.

He said he was particularly struck by the image of a young Egyptian protester standing in the street to block an armored vehicle, a pose similar to a Chinese protester, Wang Weilin, whose dramatic stance in front of a tank became one of the iconic images from the Tiananmen crackdown.

“The waters of the Nile flow into the Yellow River,” Zang said.

Still, while some drew parallels between the authoritarian government here in China and those of the Middle East, there remain obvious differences. Most important, the Middle Eastern countries now facing popular unrest all share the same volatile mix of a swelling population of angry youth, widespread unemployment, and governments that lack credibility in the face of economic despair.

China’s leaders, by contrast, have staked their legitimacy on the country’s double-digit economic growth and three decades of improving living standards. China’s economy recently surpassed Japan’s as the world’s second largest, behind the United States.

And the Beijing leadership tries to engender patriotic pride and popular support through grandiose national projects, like hosting the 2008 Olympics and the 2010 Shanghai Expo, building high-speed trains, erecting towering skyscrapers and sending Chinese astronauts into space.